AskelandPhuleNotes-14. Polymer Structures

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Example 14.1 Formation of a Barium Titanate Formulation
We want to make 1000 kilograms of BaTiO3 ceramic from BaCO3 and TiO2. How much barium carbonate and titanium dioxide should be ball milled and calcined? Example 14.1 SOLUTION Even though the actual formation of BaTiO3 involves many different intermediate phases, we can write the final reaction as: BaCO3(s) + TiO2(s) BaTiO3(s) + CO2(g) Molecular weights are: BaCO3: 137(Ba) + 12 (C) + (3 16(O)) = 197 g/mol TiO2: 48(Ti) + (2 16) = 80 g/mol BaTiO3: 137(Ba) + 48(Ti) + (3 16(O)) = 233 g/mol CO2: 12(C) + 2 16(O) = 44 g/mol 13
Figure 14.2 Schematic of the jaw, rotary, crushing rollers, and hammermill crushing equipment and ball mill (grinding) equipment. (Jaw, rotary, crushing, and hammermill: Source: From Principles of Ceramics Processing, Second Edition, by J.S. Reed, p. 314, Figs. 171 and 17-2. Copyright © 1995 John Wiley & Sons, Inc. Reprinted by permission. Ball mill grinding: Source: From Modern Ceramic Engineering, by D.W. Richerson, p. 387, Fig. 9-3. Copyright © 1992 Marcel Dekker, Inc.)
©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning ™ is a trademark used herein under license.
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Figure 14.3 Different techniques for processing of advanced ceramics.
The Science and Engineering of Materials, 4th ed
Donald R. Askeland – Pradeep P. Phulé
Chapter 14 – Ceramic Materials
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Objectives of Chapter 14
To examine the synthesis, processing, and applications of ceramic materials. Recapitulate processing and applications of inorganic glasses and glass-ceramics.
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Section 14.4 Powder Processing
Powder metallurgy - Powder processing routes used for converting metal and alloy powders into useful shapes. Reaction bonding - A ceramic processing technique by which a shape is made using one material that is later converted into a ceramic material by reaction with a gas. Tape casting - A process for making thin sheets of ceramics using a ceramic slurry consisting of binders, plasticizers, etc. The slurry is cast with the help of a blade onto a plastic substrate. Injection molding - A processing technique in which a thermoplastic mass (loaded with ceramic powder) is mixed in an extruder-like setup and then injected into a die to form complex parts. In the case of ceramics, the thermoplastic is burnt off. 15
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©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning ™ is a trademark used herein under license.
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Figure 14.1 Typical steps encountered in the processing of ceramics.
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Figure 14.4 (c) Different diffusion mechanisms involved in sintering. The grain boundary and bulk diffusion (1, 2 and 5) to the neck contribute to densification. Evaporation-condensation (4) and surface diffusion (3) do not contribute to densification. (Source: From Physical Ceramics: Principles for Ceramic Science and Engineering, by Y.M. Chiang, D. Birnie, and W.D. Kingery, Fig. 5-40. Copyright © 1997 John Wiley & Sons, Inc. This material is used by permission of John Wiley & Sons, Inc.)
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Chapter Outline
Applications of Ceramics Properties of Ceramics Synthesis of Ceramic Powders Powder Processing Characteristics of Sintered Ceramics 14.6 Inorganic Glasses 14.1 14.2 14.3 14.4 14.5
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Section 14.1 Applications of Ceramics
Ceramics are used in a wide range of technologies such as refractories, spark plugs, dielectrics in capacitors, sensors, abrasives, magnetic recording media, etc. The space shuttle makes use of ~25,000 reusable, lightweight, highly porous ceramic tiles that protect the aluminum frame from the heat generated during reentry into the Earth’s atmosphere.
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Table 14-1 (Continued)
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Section 14.2 Properties of Ceramics
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Section 14.3 Synthesis of Ceramic Powders
Slip casting - Forming a hollow ceramic part by introducing a pourable slurry into a mold. Green ceramic - A ceramic that has been shaped into a desired form but has not yet been sintered. Leaching - A process in which acids or alkalis are used to dissolve a mineral, conducted typically to get the metal or mineral of interest in solution. Calcination - Heating of chemicals to decompose and or react with different chemicals; used in traditional synthesis of ceramics.
Figure 14.4 (a) Uniaxial powder compaction showing the die-punch assembly during different stages. Typically, for small parts these stages are completed in less than a minute. (Source: From Materials and Processes in Manufacturing, Eighth Edition, by E.P. DeGarmo, J.T. Black, and R.A. Koshe, Fig. 16-4. Copyright © 1997 Prentice Hall. Reprinted by permission Pearson Education, Inc.) (b) Microstructure of a barium magnesium tantalate (BMT) ceramic prepared using compaction and sintering. (Courtesy Heather Shivey.)